1. Field of Invention
The present invention relates generally to an automatic feeder for feeding bars of raw material, i.e., bar stock to a machining tool. More particularly it relates to an automatic feeder for feeding bars to a machining center whether the bar stock is vertically oriented or horizontally oriented and for gripping and holding the bar stock during machining thereof. The present invention also provides for control interfacing of a bar stock feeding and holding mechanism with the control system of an automated machining center, such as a CNC machine either directly or by means of a sequencer system, to enable controlled actuation of the bar stock feeder and holding mechanism by the programmable control system of the machining center and to thus permit sequential machining of multiple parts from the multiple bar stock sections being supported for machining by the machining center.
2. Description of the Prior Art
When processing a plurality of raw material bars or bar stock with an automated programmable machining center, such as a CNC mill, a machine, operator in charge of the machining process must mount each of the sections of bar stock individually for processing by the machine. In many cases the machine operator must position each bar for machining after a preceding part has been completed and cut from the bar. This means that a machine operator must be attending the machine very regularly in order to machine a number of parts from a group of bars. Otherwise the mill or other machine will stand idle for significant periods of time and the bars will not be timely machined and the productive capacity of the machine will not be fully utilized. Many machined parts, require a number of different tool configurations. Since each part is individually machined from the bar stock, the number of tool changes required to make a chosen number of parts is the number of chosen parts times the number of different tooling configurations. All of the tooling changes can greatly increase the amount of time required to make the requisite parts.
Therefore, there is a need to provide an automatic bar feeder for feeding bar stock to a machining center and for supporting the bar stock during machining activity so that a user only has to set up the system and the feeder will continue to process a plurality of bars until the bar of raw material has been exhausted. Optimally, the system can also be set to process the bars as a group, performing each step on all of the bars present prior to changing the tooling, thereby significantly decreasing the machining time necessary. When the machines are CNC machines, set for milling operations, it is desirable that the bar stock be supported in vertically oriented fashion and movable by the computer controlled bed or work support table of the machine. It is also desirable that a milling head having multiple tools thereon be indexed to machining position for machining of parts from the bar stock. Unfortunately, to the detriment of CNC milling operations, the presence of a work supporting and positioning table beneath the machine support and positioning turret required the bar stock to be relatively short as compared to bar stock utilized in horizontal lathe type machines. This requirement typically causes a machine operator to make frequent bar stock changes, thus causing the productivity of the machine to accommodate the operator time that results from these frequent bar stock changes. Thus, it is desirable to minimize the operator time that is normally involved to install new bar stock at the end of a part machining cycle and thus enhance the productivity of the machine.
In keeping with the foregoing discussion, the objective of the present invention is to provide a bar feeder system having multiple work positioning stations for automatically feeding bars to a machining center. The bar feeder system of the present invention provides a plurality of mechanized chuck mechanisms for simultaneously holding a plurality of bars, four bars in the example shown, of raw material. Though the bar feeder system is designed for and discussed herein as having four work feeding and supporting chuck devices, such is not intended to be considered limiting of the spirit and scope of the present invention. The bar feeder system may more than four or less than four work supporting chuck mechanisms if desired. For positioning of the bar stock for machining, a spring loaded lifter mechanism is mounted to the machine turret and, when positioned above and in registry with the bar stock, is operated along the Z axis to grasp the upper end of a selected bar and to raise it as the bar is released by its chuck, after which the bar is again gripped by the chuck mechanism for that particular bar. As the positioned bars are machined, the mill completes each step of the machining process serially on each chuck supported bar prior to switching tooling to perform the next part machining step, thereby minimizing the time for the tool positioning sequences of the tool support and positioning turret of the machine and significantly decreasing the time necessary to complete a plurality of parts.
In keeping with the above discussion, the present invention takes the form of a machining center controlled bar feeding and holding mechanism having a base plate, which is mounted to the machine table. Attached to the base plate is a pedestal having a bar feeder top plate attached thereto. A plurality of clamping units, each being in the form of a mechanized collet chuck such as a pneumatically actuated chuck, is mounted in each corner or at other selected locations on the top plate. Each clamping unit is configured to hold a bar of raw material during machining thereof and to release the bar stock to permit its movement to a selected position relative to its chuck or to permit its replacement by fresh bar stock. Other objects and advantages of the invention will no doubt occur to those skilled in the art upon reading and understanding the following detailed description along with the accompanying drawings.
The bar feeder of the present invention is designed to allow automatic bar feeding and machining in vertical machining centers (VMCs) and horizontal machining centers (HMCs). The bar feeder may be used with machining centers in which the table rotates or is translated along X and Y move axes to position the work for machining and where the milling head either moves or is indexed to position selected machining tools for machining of the bar. The system could even be designed to rotate on the table top. A quick connect or other style connection or umbilical cable is used to connect control cables between the control of the machining center to the bar feeder to thus permit control of the chuck mechanisms of the bar feeder by the programmable control of the machining center. As necessary or desirable, an electronically controlled sequencer unit having electrical controls and electrically controlled pneumatic valves is controlled by the machining center to provide for selective actuation of the bar stock clamping mechanisms The bar feeder has a pedestal mounted on a base plate that can be bolted to a machine""s table. The pedestal has an upper pedestal plate, to which is attached a bar feeder top plate to the pedestal. The bar feeder top plate has clamping units at each of the four corners. Collets in each clamping unit allow bar stock to be loaded, four bars at a time, one bar in each corner. The air-operated collet closers are independently controlled by the machine""s programmed M functions. Currently, electro-pneumatic 5C collet closers are used, which are capable of receiving and supporting bar stock up to one inch in diameter, however, any other suitable collet or clamp may also be used for feeding and support of bar stock of lesser or greater dimension. The collets of the chuck mechanisms may be changed out as desired for adapting the clamping assemblies for differing sizes of bar stock.
On a typical vertical machining center, bars that are 12 inches long can be accommodated, depending on the height of the Z axis. Larger machines will allow longer bars to be loaded (A Hass VF3 vertical machining center, for example, will accommodate bar stock up to 16 inches long). On a horizontal machine with a stationary table, bar stock having a length up to 12 feet can be loaded, as long as there is room for the bar stock to extend beyond the back of the machine. The present invention may be used in combination with any of these machines.
A machine spindle of the machining center loads a bar puller from the tool changer or rotates a tool support and actuation turret to position the bar puller above and in registry with the selected bar. The bar puller may then be moved in programmed X and Y travels to locate above the center of the collet. Using the Z-axis, the bar puller secures the bar and pulls it up to a programmed length above the collet. The other three bars are pulled up in turn. The bar puller is replaced with a cutting tool from the magazine of the tool changer, and operations using this tool are performed on all four bars. After all four bars have been processed through the first step, the tool changer prepares for the next machining step. Once again, all four bars are machined through the second step. The process continues sequentially until all of the machining steps have been completed and the part is ready to be removed from the bar of raw material. The last step on each part is to use a circular saw to cut off the part, by reducing spindle speed just before the saw crosses the center of the part, the part can be separated neatly and dropped off for retrieval. These steps are repeated sequentially until the last part is cut off from each bar. Then the operator removes the nubs and loads fresh bar stock.
FIGS. 3 and 4 are bottom and cross-sectional views of the generally rectangular bottom connection plate of the bar feeder. A plurality of slots, four in the example shown, are located around the perimeter of the bottom connection or mounting plate and may be used to adjustably attach the bar feeder to the machining table of the automated machining center. Located between the slots are two alignment or indexing holes which receive indexing pins for squaring or establishing precise positioning of the bar feeder on the machine table. A plurality of connection holes ring the central opening of the base plate as shown in FIG. 2. The connection holes align with the connection holes in the bottom surface of the pedestal, seen in FIG. 6. Two indexing pin receiving holes located to either side of the central opening of the base plate and are configured to mate precisely with indexing pins that extend downwardly from the pedestal.
FIGS. 4 and 5 are elevation and sectional views respectively of the pedestal and FIGS. 6 and 7 are bottom and plan views respectively, also showing the pedestal of the bar feeder, The pedestal is of hollow and generally conical configuration as is evident from FIGS. 4 and 5. A ring of connection holes located in the bottom surface of the pedestal, seen in FIG. 6 and are located to align with corresponding connection holes in the bottom connection plate shown in FIG. 2. Located on opposite sides of the bottom surface of the pedestal are indexing openings into which indexing pins are fitted. The indexing pins are sized and configured to mate with the pin receiving holes located in the base, plate, thereby establishing precision alignment of the pedestal and base. A plurality of holes located on a recessed portion of the bottom surface are for attaching a cover plate which fits into the recess and covers the lower opening of the pedestal. A pair of umbilical cable access holes extend through the sidewall of the pedestal. The larger, upper hole is sized to receive a control umbilical cable which extends from the control of the machining center or the sequencer unit into the cavity in the bar feeder. The control umbilical cable operates the mechanisms within the cavity. The smaller, lower umbilical access hole of the pedestal is sized to receive an air line which feeds pressurized air to a plurality of air valves for air controlled operation of the collets. A plurality of connecting holes in the top surface of the pedestal are configured to mate with holes in the upper pedestal plate, seen in FIG. 9. A pair of indexing pin holes are located on the top surface of the pedestal and receive indexing pins which are sized and configured to mate with the pin receiving holes in the upper pedestal plate.
FIG. 9 is a top or plan view of the upper pedestal plate of the pedestal of the bar feeder, showing a plurality of arcuate indentations are cut from the perimeter of the upper pedestal plate. These arcuate indentations are sized and configured for alignment with circular cut-outs in the bar feeder top plate. These indentations are configured to receive the vertically oriented bars of raw material. A plurality of connection holes adjacent the perimeter of the upper plate are configured to align with matching connection holes in the top plate. The plurality of holes adjacent the outer ring of holes are aligned with the holes in the top plate to which the clamping units are attached. An inner ring of holes is formed of smaller and larger openings. The four smaller openings are configured to align with the four connecting holes in the top plate. The larger holes are for sized to receive air hoses entering the pedestal.
FIG. 1 is a perspective view of the pedestal with the upper plate located thereon. The pedestal and upper plate are mounted on the base plate though the upper pedestal plate is not visible in FIG. 1.
FIG. 8 is a bottom of the top plate of the bar feeder, showing its relationship with the pedestal top plate of FIG. 9. The pedestal top plate is mounted to the pedestal by mounting bolts extending through a plurality of connecting holes. One set of connecting holes forms a ring about the central portion of the bar feeder top plate and mates with the holes, located around the perimeter of the upper plate of the pedestal. An additional four connecting holes are oriented to form a square, shown in FIG. 8, that is centered within the outer ring of connecting holes. Located near each of the four corners are rings of connection holes which receive mounting bolts for connecting each of the clamping units to the upper surface of the bar feeder top plate. The clamping unit connection holes form a circular array around circular bar stock cut-outs or openings which are sized to receive the vertically oriented bars of raw material. Located near the circular array of clamping unit connection holes are two small air inlet holes for providing air to the collets of the clamping units.
FIGS. 10-13 are top, bottom, cross-sectional and detail views of the clamping unit chuck. The chuck assembly includes a housing of hollow and generally conical configuration. A plurality of holes extending longitudinally through the sidewalls of the chuck receive connection bolts for connection of the chuck to the bar feeder top plate. The detail drawing of FIG. 13 shows a close-up of an air inlet notch for admitting compressed air from an air supply shown in the schematic illustration of FIG. 14 which connects with each air chuck mechanism via air control valves which are actuated by a sequencer system responsive to control signals of the control system of the machining center. Located adjacent the central opening of the chuck is a ring of three cylinder guide mounting holes. The chuck is sized to receive any one of a plurality of collet sizes.
The parts of the present invention are preferably made of anodized aluminum, but other metals, plastics, etc. may be used is preferred, The parts are connected using any standard attachment means such as screws, bolts, etc.
The system offers more than increased productivity for machining centers, it allows many workpieces to be processed on a mill in less time than on a lathe. Higher spindle speeds are generally available on a mill and fewer tool changes are required when milling. For example, a typical 10-hp VMC offers spindle speeds starting at 7,500 rpm compared to 4,000 rpm for lathes with a 1-inch bar capacity. Whereas a lathe processes one part at a time, repeating all tool changes for each part, a machining center with the present invention changes tools only after it has performed operations on all four parts, thereby saving time. For example, in one instance the present invention could make four parts in three minutes on a mill, whereas made on a lathe a single part could take six minutes.
Parts requiring live tooling on a turning center may also benefit from using a mill with the present invention. Live tooling on a lathe may provide only limited speeds and feeds compared to those provided by a machining center""s main spindle. Circular interpolation on the machining center allows holes and threads to be milled easily. Likewise, operations performed off center are obviously no problem on the mill. In some cases, operations that produced tangles of stringy chips on a lathe created no such problems when milled instead.
Small, intricate parts, such as for the medical and aerospace fields, are especially well-suited for the present invention. Aluminum parts normally run in turning centers can be machined faster in mills due to higher rpms and 75% fewer tool changes. And, when not bar feeding, the present invention provides a pallet of collet closers that can be used for other work such as for robotic loader and unloader operations.
The size of the present invention may be increased or decreased depending on the needs of the user and the size of the machining center.
Many features have been listed with particular configurations, options, and embodiments. Any one or more of the features described may be added to or combined with any of the other embodiments or other standard devices to create alternate combinations and embodiments.
Although the examples given include many specificities, they are intended as illustrative of only one possible embodiment of the invention. Other embodiments and modifications will, no doubt, occur to those skilled in the art. Thus, the examples given should only be interpreted as illustrations of some of the preferred embodiments of the invention.
So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the preferred embodiment thereof which is illustrated in the appended drawings, which drawings are incorporated as a part hereof.
It is to be noted however, that the appended drawings illustrate only a typical embodiment of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.